Bonding

Ionic Compounds are held together by forces of attraction between oppositely charged ions.

Ionic Compounds are usually formed when metals react with non-metals.

Metals form positive ions

Non-Metals form negative ions

Group 1 form 1+ ions

Group 9 form 1- ions

Atoms want to acheive a full outer shell.

MgO = Mg²⁺ and O^2-

Not all atoms have the right amount of atoms they are willing to swap though:

CaCl₂ = Ca²⁺ and Cl^-

There are many strong ionic bonds that hold giant ionic structures together.

This means that it is very hard to break these bonds.

Therefore they have high melting points and boiling points and are solids at room temperature.

A solid ionic compound cannot conduct electricity as the particles cannot move around.

A molten ionic compound can conduct electricity.

Most compounds will dissolve in water and can then conduct electricity.

Covalent Bonds are formed when atoms of non-metals share pairs of electrons with each other.

Metals normally need to gain electrons to become stable.

They can share electrons so that they both gain.

Sometimes there are different numbers of electrons, so more atoms become involved, like H₂O.

Most substances containing covalent bonds are simple molecules.

These have low melting and boiling points as there are weak forces between molecules.

They have no overall charge, so cannot carry an electrical charge.

You can use models to understand bonding, but they are limited.

However, some, like diamonds, are giant covalent structures which make them very hard.

Each carbon atom shares 4 covalent bonds with its neighbours.

Graphite is different to diamond, as it has layers of bonded carbon atoms.

These layers can slide easily over each other, making graphite soft and slippery.

Graphite conducts electricity, as there are dislocated electrons able to move along the layers.

Fullerenes are also carbon atoms but that form large hollow cages of hexagonal rings.

They can be used for drug delivery inside the body, lubricants or catalysts.

Graphene is only a single layer of graphite, one atom thick.

They are a layer of interlocking hexagons.

You can use tape pulled off graphite to create graphene.

It is an excellent conductor of electricity as it has a very low density.

It is the most reactive of all the carbon forms.

Graphene will be used to further the electronics industry.